Dynamo-electric machine construction



y 1933- W. G. SCHNEIDER 7 1,917,552

DYNAMO ELECTRIC MACHINE CONSTRUCTION Filed Nov 1928 gmunfo'c \AMJAM QTDQHNEWEY,

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Patented July 11, 1933 UNITED STATES PATENT OFFICE WTLLIAM G. SCHNEIDER, OF MAUMEE, OHIO, ASSIGNOR TO ELECTRIC AUTO-LITE COMPANY, OF TOLEDO, OHIO, CORPORATION OF OHIO DYNAMIC-ELECTRIC MACHINE CONSTRUCTION Application filed November 2, 1928.

This invention relates to dynamo-electric machines and more particularly to the field structure of machines of this character.

It is well known in the art that in order to reduce or obviate magnetic humming or noise it has been the practice to arrange the armature slots and teeth out of parallelism with the axes of the armature so as to provide a gradual entering of the teeth under the tip of the pole piece.

This invention contemplates a structure wherein it is not essential to use an armature having, its teeth out of parallelism with its axis in order to reduce magnetic humming. It also embraces an embodiment of frame and pole structure for dynamo-electric machines providing a substantially concentric air gap between the armature and the pole pieces, each pole piece having structural characteris tics such that magneticnoise or humming due to an abrupt flux density .variation or variations caused by rapid changes of reluctance of the magnetic circuit upon entering and leaving of armature teeth adjacent the face of the polepiece is reduced by a gradual increase of reluctance in the magnetic path toward the tips of the pole pieces.

This gradual increase in magnetic reluctance is accomplished by progressively reducing the cross sectional area of the poles from a point at or between the axis thereof and the tips of the same, thus making possible a gradual variation of flux density.

It has for an object to increase as much as possible the contact surface between the frame and the pole piece proper so to avoid or prevent the choking of the lines of magneticforce thereby reducing a wasteful resistance in the magnetic circuit and permitting a decrease in the ampere turns required to excite the field poles for a predetermined magnetic density, the arrangement affording a means for rapidly dissipating or radiating the heating set up by the eddy currents in the poles and the heat generated in v the field coils.

Serial No. 316,?47.

readily and easily assembling the pole piece and frame structure.

Further objects and advantages are within the scope of this invention such as relate to the arrangement, operation and function of the related elements of the structure, to i arieus details of construction and to combinations of parts, elements per se, and to economies of manufacture and numerous other features as will be apparent from a consideration of the specification and drawing of a form of the invention, which may be preferred, in which:

Figure 1 is a side elevational view of a dynamo-electric machine embodying my inven- Figure 5 is an lsometric view showing a modified form of the pole piece;

Figure 6 is an isometric view showing one of the energizing field coils;

Figure 7 is a fragmentary detail view showing another method of securing the pole piece to the frame.

Referring to the drawing the dynamo-electric machine with which I have shown my invention comprises a casing 5within which is revolvably supported an armature 2 secured;

upon a shaft 7. Secured to the casing 5 of the machine and spaced at regular intervals is a plurality of pole pieces 10, each pole piece being surrounded by an energizing field coil 11. The pole pieces are adapted to be secured r to the casing 5 by means of rivets 14:, however it is to be understood that the pole pieces may be secured to the casing in any suitable mariner.

Referring particularly to Figure 3, each pole piece 10 is formed of a straight bar of material 15 shown in dotted lines, which is subsequently formed int-o a curved section or segment as shown in full.

I have illustrated the strip from which the pole piece is formed as preferably provided with the diverging sides, but it is to be understood that the sides may be parallel, and after forming the section, portions of the sides thereof may be removed to produce the configuration shown in full lines in Figure 3.

It may be found desirable to secure the pole pieces to the casing 5 by welding as at 21 particularly shown in Figure 7, and to this end projections 19 may be struck up from the upper curved surface of the pole piece. During the welding operation these projections will be caused to melt away as at 21 so that at the completion of the operation, the upper curved surface is in intimate engagement with the walls of the casing.

I have found that if the pole piece is formed with sharp or feather edges 20, i. e. the edges formed by the intersection of the side surfaces and the curved lower face of the pole piece adjacent the armature, that the so-called magnetic humming action due to the abrupt cutting of the lines of force by the armature is materially decreased. It is particularly desirable tohave the sharp edges of the pole piece overlap the slots in the armature so that the pole piece edges are at no time, during the operation of the device, in registratlon with opposing armature slots. In other words, the polar span of the pole piece is such that both edges of said polar face are out of simultaneous registration with armature slots or when one edge of a pole piece is in registration with an armature slot, the otheredge is in registration with at least a portion of an armature tooth.

It will be apparent that the area of the lower surface of the pole piece in proximity with the surface of the armature approximates the area of the pole piece in contact with the casing of the machine thus providing an eflicient path for the passage of the magnetic lines of force through the pole pieces and the casing of the machine. This type of construction also decreases the magnetic reluctance presented to the magnetic lines of force produced by the field coil 11, and also decreases the heating effects set up by eddy currents in that an additionl metallic path is provided for dissipating and radiating the heat.

I have found that by rounding the side faces of the pole piece 10 as shown particularly in Figure 5, that the magnetic humming action is further decreased.

In Figure 6 is shown a formed field coil before its application to the pole piece, the coil being held in its proper position by means of pins 12 driven into the end faces of the pole piece, but it is to be understood that the coils may be held in place by any suitable means.

The construction of a pole piece as hereinbefore described permits the use of high grade rolled steel, and the casing 5 may be a section of steel tubing cut into proper length thus effecting a material decrease in the cost of manufacturing and permitting the utilization of the material possessing high magnetic characteristics. Furthermore, this construction permits the assembly of the pole pieces and frame before the coils are put in place. This arrangement makes it possible to machine or finish the inner surfaces or polar faces of the pole pieces at a greater rate of speed than has heretofore been possible as a cutting or cooling compound may be used during the machining operations because the coils are not present. In this construction the increased area of the pole piece in contact with the frame insures a proper alignment of the pole piece and frame so that a uniform air gap may be had between the pole pieces and armature. In event that the field coils become defective or break down, they may be easily removed and new ones substituted by merely extracting the retaining pins 12.

It is apparent that, within the scope of the invention modifications and different arrangements may be made other than is herein disclosed, and the present disclosure is illustrative merely, the invention comprehending all variations thereof.

What I claim is:

. 1. In a dynamo-electric machine a curved frame formed of steel, an armature having peripheral teeth and slots; a plurality of separate pole pieces secured to said frame, said pole pieces comprising an arcuate shaped section of rolled steel, said pole section having its back surface portion curved to intimately contact against a portion of the inner surface of said frame, a polar face portion having a zone substantially concentric with the axis of the dynamo-electric machine, substantially flat side surfaces intercepting said polar-surface at acute angles, both edges of said polar face being out of simultaneous registration with armature slots.

2. In a dynamo-electric machine a curved frame formed of steel, an armature having peripheral teeth and slots, a plurality of separate pole pieces, said pole pieces comprising an arcuate shaped section formed of rolled steel, said pole having a back surface portion curved to intimately contact against a portion of the inner surface of said frame, the area of said back and polar surfaces being substantially equal and having flat side surfaces intercepting said polar face at acute angles, the polar span of said pole being such with respect to the armature that when one edge of said pole face is in registration with an armature slot the other edge is in registration with at least a portion of an armature tooth. i

3. In a dynamo-electric machine, a curved frame formed of steel; an armature having peripheral teeth and slots; a plurality of separate pole pieces, said pole pieces comprising an arcuate shaped section of rolled steel, said pole section having its back surface portion curved to intimately contact against the portion of the inner surface of said frame; a polar face portion having a zone substantially concentric with the axis of the dynamo-electric machine, said pole section having flat side surfaces intercepting said polar face at acute angles forming feather edges with the pole face of the section, the polar span of said pole being such With respect to the armature that when one feather edge of said pole face is in registration With an armature slot, the other edge is out of registration with at least a portion of an armature slot whereby magnetic hum is substantially eliminated.

4. A solid pole piece for dynamo-electric machines having a cylindrical frame substantially of steel and an armature having peripheral teeth and slots comprising an arcuate shaped section of rolled steel, said pole having a back surface portion of a curvature to substantially coincide with and intimately contact against a portion of the cylindrical frame, the polar face portion having a zone substantially concentric with the aXis of the dynamo-electric machine, said pole piece having flat side surfaces intercepting said polar surface at acute angles to form feather edges, the polar span of said pole being such with respect to the armature that both edges of said polar face are out of a simultaneous registration with the armature slots.

In testimony whereof, I affix my signature.

W'ILLIAM G. SCHNEIDER. 

